public static class vec2d
{
  public float x, y;

  vec2d()
  {
    this.x = 0.0;
    this.y = 0.0;
  }

  vec2d(float x, float y)
  {
    this.x = x;
    this.y = y;
  }

  vec2d(vec2d v)
  {
    this.x = v.x;
    this.y = v.y;
  }

  void add(vec2d v)
  {
    this.x += v.x;
    this.y += v.y;
  }

  void add(float x, float y)
  {
    this.x += x;
    this.y += y; 
  }
}
